The growing concern for protecting natural resources has prompted various initiatives, one of which is a drive to incorporate renewable resources into gasoline. Adding methanol or ethanol to gasoline to boost the octane number is an example of a response to this need to conserve finite resources. However, a major drawback to this practice is that the alcohol cannot be added prior to the gasoline being transported through a pipeline since the alcohol is water-soluble and will extract out of the gasoline and into any water that might be present in the pipeline system or storage tanks. The present invention provides an alternate method that achieves the conservation goal. Furthermore, the resultant blended gasoline may be transported through a pipeline without the loss of octane number boosters. According to the present invention, ethanol, which is a renewable resource since it may be produced from corn, undergoes etherification with propylene to produce isopropyl ethyl ether (IPEE) which may then be blended into gasoline. An additional benefit of blending ethers into gasoline to boost the octane number is that ethers generally have lower Reid vapor pressures than alcohols, and lowering the Reid vapor pressures of gasoline is another environmentally driven goal.
The octane number of IPEE is less than another commonly used octane number booster, diisopropyl ether (DIPE), which has an octane number of about 105, (R+M)/2. DIPE and IPEE are produced in similar manners, and being able to produce them concurrently satisfies both the desire for high octane number boosters and the need to incorporate a renewable resource into the gasoline. Furthermore, the gasoline after being blended with DIPE and IPEE, may be transported through pipelines since the ethers are not very water soluble.
The art shows various processes for the production of ethers. For example, U.S. Pat. No. 4,906,787 discloses a process where in a reaction zone at least one light olefin is hydrated to form at least one alcohol which then undergoes etherification with the olefin to produce an ether. Unreacted alcohol is recycled to the reaction zone. It is important to note that in this patent all the alcohol that is reacted with the olefin to form ether is produced within the process. No external source of alcohol is used. Similarly, U.S. Pat. No. 4,857,664 and U.S. Pat. No. 4,935,552 disclose processes for producing ether from starting reactants of a light olefin and water. No external sources of alcohol are used. In contrast, U.S. Pat. No. 4,714,787 discloses producing an ether, methyl isopropyl ether, from methanol and propylene. In U.S. Pat. No. 4,714,787, all the alcohol used in the process is provided through an external source with no alcohol being generated within the process. Finally, U.S. Pat. No. 4,503,263 discloses a process for producing ethers in the presence of acidic superacid catalysts using either (1) an olefin and water, (2) an alcohol, or (3) an olefin and an alcohol as reactants. In the case where an olefin and water are the reactants, the olefin would be hydrated to form an alcohol which would then undergo etherification with the olefin to produce an ether. Where only alcohol is the reactant, bimolecular dehydration of the alcohol would occur to form the ether. Where an olefin and an alcohol are the reactants, the alcohol undergoes etherification with the olefin to form an ether.
The present invention maintains the goal of producing a high octane number product at a low cost by using propylene, a low cost material, and water to form isopropyl alcohol which is then reacted with propylene to form DIPE. At the same time, the invention achieves a goal of incorporating a renewable resource into gasoline by concurrently using ethanol from an independent source as a reactant to form IPEE.